This study intended to clarify the realities of critical thinking of South Korean high school students in science learning. A 42-question survey was conducted on 156 1st-year South Korean high school students to achieve this end.The results indicated that, as well as having a strong curiosity about phenomena, students collect as much experimental data as possible, carefully ascertain cause and thoroughly examine and interpret results. The results also showed that students tend to focus on the collection of experimental data and its interpretation more so than the validity and reproducibility of the experiment and that there is an issue in that they lack a healthy skepticism for things.In addition, the causal relationship of “the deeper a student thinks about things and the more they ascertain the significance and essence, the more carefully they collect experimental data and examine its interpretation” was also clarified as a factor structure that influences the critical thinking of students. At the same time, the causal relationship of “the more inquisitive the student, the more they think about things with a healthy skepticism and without blindly accepting external information, focus on the validity and reproducibility of the experiment and reflect on their own ideas and actions” was also clarified.